The invention relates to electronic prepress and imagesetting systems. More particularly, the invention relates to a method and apparatus for digitally modifying raster data, defined as image data which has been processed by a raster image processor.
Printing presses use plates to print ink onto paper and other media. One method used for creating plates has been to expose photosensitive film with the matter to be printed. When the film is developed, the matter imaged on the film is imaged onto a photosensitive plate, sometimes referred to as xe2x80x9cburningxe2x80x9d a plate. After processing, the plate can be used to print the matter onto a medium.
In a black and white printing job, there is usually one plate that is used to print black ink. In a color printing job, a different plate is used for each color ink. Typically, a color job will use three colors of ink: cyan, magenta, and yellow. This is because a combination of cyan, magenta, and yellow can be used to make other colors. A plate is produced for each color ink. Often, in addition to cyan, magenta, and yellow, black ink is also used. An additional plate is then required to print the black ink. Occasionally, one or more colors will be printed separately as well, referred to as a xe2x80x9cspot color.xe2x80x9d That color will also have its own plate.
Electronic prepress systems have used an imagesetter to receive raster data for imaging onto photosensitive film. The film is then used to create a plate. The imagesetter exposes the photosensitive film pixel by pixel, for instance, by scanning a laser across and down a piece of film. Electronics controls the laser to expose, or refrain from exposing, each pixel in the raster data in a precise and repeatable manner. Recently, platesetters also have been used to create plates directly from raster data without the use of film. Imagesetters, platesetters and other output devices for printing are generally referred to as print engines.
Print engines typically have been served by a dedicated raster image processor (RIP) connected between the print engine and a xe2x80x9cfront endxe2x80x9d computer running imaging application software such as Quark Express(trademark) and Adobe Pagemaker(trademark),. Exemplary front end computers run on operating systems such as Windows NT(trademark). MacOS(trademark) and UNIX(trademark). In a typical configuration, a Macintosh(trademark) front end is connected to a RIP which is coupled with an imagesetter. The RIP interprets the graphic information transmitted to it by the front end computer, and converts the graphic information into raster data that can be imaged by the print engine. The raster data produced by the RIP is configured to match required parameters of both the imagesetter and the media. The imagesetter parameters include imaging resolution, processing speed and specific printing capabilities. The media parameters include the length, width and thickness of the media, as well as the chemical makeup of the photosensitive layer.
Typically, the imaging application software provides output in the format of a page description language (PDL) such as Postscript(trademark) and PDF(trademark) offered by Adobe Systems of Mountain View, Calif. Page description languages describe images using descriptions of the objects contained in the page. Use of page description languages allows pages to be described in a way that can be interpreted appropriately for imaging at various sizes and resolutions. PDL code is generally significantly smaller in data size than the raster data that results from interpreting the PDL code. Use of a page description language therefore allows for faster file transfer. Also, page description languages are machine-independent so that any print engine or other device which understands the PDL can produce an image therefrom.
When PDL image data is received by the RIP, operations performed by the RIP, such as using fonts to lay out text and color processing to create raster data for each color, typically results in one or more raster data bit maps. The raster data produced by the RIP is binary, meaning that each pixel is either on or off. The raster data for each of the colors in a color image is referred to as a color separation.
Each color separation is transferred from the RIP to the output device over a high speed interface. This has historically been a parallel data transfer interface that provides a data transfer rate sufficient to keep the output device operating at a desired operating speed. Typically, the process of RIP processing data to prepare bit map image files for transfer to the output device has been slower than the imaging speed of the output devices. The slower RIP processing speed sometimes causes the output device to remain idle while waiting for a RIP to prepare the next bit map image file. The print engine is generally an expensive capital investment, so full time utilization of the print engine is desirable. Keeping the print engine busy is therefore a goal of modem electronic prepress system design.
The use of a RIP multiplexer (MUX), for example the MULTISTAR(copyright) offered by Agfa Division of Bayer Corporation of Wilmington, Massachusetts, offers the electronic prepress industry some improvement in data throughput, and associated cost savings, by functioning as a data buffer between one or more RIPs and a print engine. Cost savings and improved efficiency have been realized by either RIP processing an image with a first RIP while transferring a previously RIP processed image to the output device or by storing RIP processed raster data for transfer to the output device at an appropriate time after RIP processing. This multiplexer more fully utilizes the output device, and therefore provides increased throughput.
Typically, for prior art electronic prepress systems, a specific output device configuration had to be connected to the RIP before a job could be processed. For example, a print job requiring that a particular type of imagesetter be used for an output device, or that a particular media type or size be loaded onto the output device, could not be RIP processed into raster data if the particular output device connected to the RIP did not meet the job requirements. Improper output device configuration caused delay or, more frequently, required that a user take some action to physically change the output device connected to the RIP in order to continue processing and outputting image files. Since the electronic and imagesetting systems of the prior art were not only device dependent but media dependent as well, the queuing of rasterized print jobs for different media or output devices was not possible. Thus, the choice of the output device and print media proved to be a considerable hindrance in productivity.
RIP processing speed has improved so that the RIP is no longer a bottleneck in the prepress workflow of single page printing jobs. As RIP processing speed has increased, however, so has the demands of output devices. Recent use of larger format imagesetters and platesetters allows multi-page press size images in film or plate, referred to as xe2x80x9cflats,xe2x80x9d to be produced that contain four, eight, or more pages in each image. These output devices also have been driven by a dedicated RIP or MUX. Because multi-page flats are complex, the RIP is often a bottleneck in creating these multi-page press format films and plates. The PDL code that must be interpreted to image multiple page flats is very complex. RIP processing time for complex images can require several multiples of the imaging time.
RIP processing time has a greater impact on workflow when a change is required in a complex image. This is because a change in even a part of one page of a multi-page flat generally requires that the entire image be reprocessed by the RIP. The bottleneck of slow RIP speeds for complex images affects the workflow both the first time the flat is processed by the RIP and the second time when a modified version of the image is processed.
One alternative to reprocessing the entire image, when a modification to a RIP processed image is desired, is to physically modify a film that is output by an imagesetter to make a plate. To accomplish this modification, a portion of the image to be modified is physically cut from the film, and if necessary, a correction film is inserted in its place. This can be difficult to accomplish without imaging artifacts. More importantly, this alternative is not possible with direct-to-plate, i.e. computer-to-plate, technology.
Another technique to modify images once they have been processed by the RIP is known as doubleburning. To conventionally doublebum an image onto a plate is to create two pieces of film and create the plate from both of the images. In other words, the photosensitive plate is physically exposed to two pieces of film, and the resulting plate includes the images from both pieces of film. This is particularly useful for producing composite images where one part of the image has several possible versions. An example of such a composite image contains graphics and text, with different versions of text to be imaged with the same graphics. It can be time consuming to reprocess the complex graphics with each of the variations of text. One technique to reduce RIP processing time is to image graphics once onto a film, leaving a blank space where the particular variation of text is to be inserted into the image , then imaging the text separately onto a second film, without the need to again image the graphics. A plate having both the graphics and one version of the text is produced by burning the plate twice, once with the film containing only the graphics, and once with the film containing only the text. This doubleburning technique is unavailable in direct-to-plate technology since film is not used in the direct-to-plate process of making plates.
The invention relates to a print drive-which is electronically connected between one or more raster image processors and one or more destination devices. The print drive receives, stores, and transmits raster data of an image processed by the RIP. In one embodiment, the print drive combines raster data of two separate images with a digital doubleburner. In another embodiment, the print drive masks a section of raster data by using masked raster data to delineate the area to be masked. In yet another embodiment, the print drive modifies first raster data by masking the first raster data with masked raster data and then combining the first raster data with the masked first raster data. In each case, the raster data from two separate images is combined with a digital image combiner, i.e. a doubleburner or a mask or a combination of the two.
In general, the invention relates to a method for imaging. The method includes receiving first raster data of a first image processed by a first RIP, and second raster data of a second image processed by a second RIP. Actually the first and second raster data can be processed by the same RIP, or by separate RIPs as desired. The first and second raster data are combined to form combined raster data representing a resultant image.
In one embodiment the method includes the step of receiving, from a second raster image processor, second raster data of a second image which represents a modification to the first image, and mask raster data of the second image which represents a mask of the modification to the first image. The method also includes digitally masking the first raster data with the mask raster data to form masked first raster data. Finally, the method includes digitally combining the masked first raster data and the second raster data to form modified raster data representing a resultant image.
In one embodiment, the first RIP and the second RIP are the same RIP. In another embodiment, the first and second images are each either a color image or a greyscale image. In another embodiment, the method further includes rendering the raster data to a destination device, such as: a platesetter for rendering a resultant image onto a printing plate; an imagesetter for rendering a resultant image onto photosensitive paper, film or other media; a printer for rendering a resultant image onto paper or other print media; a memory for storing the raster data in a file or buffer; or any other known device or application capable of receiving raster data. In another embodiment, the RIPs are page description language interpreters.
In another embodiment, the method further includes creating a first image file coded in a page description language, transmitting the image file to a first RIP which then interprets the first image file to produce the first raster data, and thereafter transmits the first raster data to an output device. The method also includes creating a second image file coded in a second page description language, transmitting the image file to a second RIP which produces the second raster data, and thereafter transmitting the second raster data to an output device. In another embodiment, the method also includes receiving the first image file by a first image server, storing in the first image server the first image file, and transmitting by the first image server to the first RIP the first image file. The method also includes receiving the second image file by a second image server, storing in the second image server the second image file, and transmitting by the second image server to the second RIP the second image file.
In general, in another aspect, the invention features a print drive system including a print drive. The print drive includes a print drive input terminal receiving first raster data of a first image processed by a first RIP, and a second raster data of a second image processed by a second RIP. A digital doubleburner is electrically coupled to the print drive input terminal. The digital doubleburner digitally combines the first raster data and the second raster data to form combined raster data of a resultant image.
In one embodiment, the print drive receives second raster data and mask raster data of a second image processed by a second raster image processor. The print drive also includes a digital masker in electrical communication with the print drive input terminal. The digital masker digitally masks the first raster data with the mask raster data to form masked first raster data. The digital doubleburner combines the masked first raster data and the second raster data to form modified raster data of a resultant image.
In another embodiment, the print drive system includes a graphics imaging system in electrical communication with the print drive input terminal. The graphics imaging system includes a general purpose computer having imaging software for producing first and second image files coded in PDL. The graphics imaging system also includes a RIP in electrical communication with the general purpose computer. The RIP includes a raster image processor receiver for receiving the first image file and the second image file. The RIP also includes an interpreter in electrical communication with the raster image processor receiver for interpreting the first image file and the second image file. The interpreter produces first raster data and second raster data. The RIP also includes a raster image processor output in electrical communication with the interpreter for transmitting the first raster data and the second raster data.
In another embodiment, the graphics imaging system includes an image server in electrical communication with the general purpose computer and the raster image processor. The image server includes an image server receiver for receiving from the general purpose computer the first image file and the second image file. The image server also includes an image server data store in electrical communication with the image server receiver. The image server data store stores the first image file and the second image file. The image server also includes an image server transmitter in electrical communication with the image server data store. The image server transmitter transmits to the RIP the first image file and the second image file.
In general, in another aspect, the invention features an imaging system. The imaging system includes an image generator creating a first image and a second image. The imaging system also includes a raster image processor in electrical communication with the image generator. The raster image processor processes the first image to create first raster data and processes the second image to create second raster data. The imaging system also includes a print drive in electrical communication with the raster image processor. The print drive digitally combines the first raster data and the second raster data to form combined raster data of a resultant image. In another embodiment, the imaging system also includes a destination device in electrical communication with the print drive. In another embodiment, the print drive masks the first raster data with the mask raster data and digitally combines the masked first raster data and the second raster data to form modified raster data of the resultant image. In another embodiment, the print drive masks the first raster data with the mask raster data. The print drive digitally combines the masked first raster data and the second raster data to form modified raster data of the resultant image.
In another aspect, the invention relates to a method for creating a modification for an original image. The method includes creating a modification image having a modification layer for correcting the original image and a mask layer for masking an area of the original image. The method requires accurate positioning between the layers . The method also includes processing the modification image to produce modification raster data and mask raster data. In one embodiment the method includes, prior to the step of creating a modification image, the steps of creating an original image, positioning the original image, and processing the original image to produce original raster data. In another embodiment, the method includes masking the original raster data with the mask raster data to substantially clear the modified area thereby forming masked first raster data. The method also includes digitally combining the masked first raster data with the modification raster data thereby creating modified raster data of the resultant image. In another embodiment, the method includes rendering the modified raster data to a destination device. The destination device is any known device or application for receiving raster data, such as: a platesetter for imaging onto a printing plate; an imagesetter for imaging onto photosensitive paper, film or other media; a printer for printing onto paper or other media; or a memory for storing the raster data in a file or buffer. In another embodiment, the mask layer comprises a substantially 100% fill mask.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description, figures and claims.